1. Field of the Invention
The present invention relates to an abnormality determination system of a filter disposed in an exhaust gas passage of an internal combustion engine.
2. Description of Related Art
In order to capture particulate matter (hereinafter, also referred to as “PM”) included in exhaust gas discharged from an internal combustion engine, a filter is disposed in an exhaust gas passage thereof. When the filter reaches an abnormal state due to destruction or the like, exhaust gas from which the PM has not been satisfactorily removed is discharged and thus a PM sensor for detecting the PM in the exhaust gas may be disposed on the downstream side of the filter so as to detect the abnormal state of the filter. Here, depending on a situation in which the PM sensor is located, a deviation occurs between the output of the PM sensor and the amount of PM in the exhaust gas and it may be difficult to appropriately detect the PM. Accordingly, in a technique disclosed in International Publication No. 2012/77182 (WO2012/77182), with a focus put on a correlation between the deviation and the exhaust gas flow rate, improvement in PM detection accuracy is achieved by correcting the output of the PM sensor using the exhaust gas flow rate as a parameter.
Japanese Patent Application Publication No. 2012-122399 (JP 2012-122399 A) discloses a configuration in which the output of the PM sensor is adjusted on the basis of the fact that the attachment of PM to a sensor element of the PM sensor varies depending on the exhaust gas flow rate.